TITLE:
An Experimental Observation of the Thermal Effects and NO Emissions during Dissociation and Oxidation of Ammonia in the Presence of a Bundle of Thermocouples in a Vertical Flow Reactor
AUTHORS:
Samuel Ronald Holden, Zhezi Zhang, Jian Gao, Junzhi Wu, Dongke Zhang
KEYWORDS:
Ammonia, NH3 Dissociation, NH3 Oxidation, Flow Reactor, Nitrogen Oxides (NOX), Thermal Effects
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.13 No.3,
July
31,
2023
ABSTRACT: Ammonia (NH3) dissociation and
oxidation in a cylindrical quartz reactor has been experimentally studied for
various inlet NH3 concentrations (5%, 10%, and 15%) and reactor
temperatures between 700 K and 1000 K. The thermal effects
during both NH3 dissociation (endothermic) and oxidation (exothermic) were observed using a bundle of
thermocouples positioned along the central axis of the quartz reactor,
while the corresponding NH3 conversions and nitrogen oxides
emissions were determined by analysing the gas composition of the reactor exit
stream. A stronger endothermic effect, as indicated by a greater temperature
drop during NH3 dissociation, was observed as the NH3 feed concentration and reactor temperature increased. During NH3 oxidation, a predominantly greater exothermic effect with increasing NH3 feed concentration and reactor temperature was also evident; however, it was apparent that NH3 dissociation occurred near
the reactor inlet, preceding the downstream NH3 and H2 oxidation. For both NH3 dissociation and oxidation, NH3 conversion increased with increasing temperature and decreasing initial NH3 concentration. Significant levels of NOX emissions were observed
during NH3 oxidation, which increased with increasing temperature.
From the experimental results, it is speculated that the stainless-steel in the
thermocouple bundle may have catalysed NH3 dissociation and thus
changed the reaction chemistry during NH3 oxidation.